He's been transported for a sore ankle and back, but nothing too bad.UPDATE: It turns out that "sore ankle and back" really meant that he fractured two vertebrae and broke his ankle, but he won't require surgery according to Jenna Fryer with the AP. And he's got a concussion.

[UPDATE]: 13 people were injured by flying debris, including two track workers who were taken to the hospital, according to the local ABC affiliate. Most of the injured were treated at the track. (Thanks JohnTheRaceFan!)